1. Technical Field
The present invention relates to customizable, metallized, flexible packaging material that can be used to balance product visibility with barrier protection in packaged food products and a method of making the customized packaging material.
2. Description of Related Art
Multi-layered flexible film structures made from polymers are often used in flexible packages where there is a need for its advantageous barrier, sealant, and graphics-capability properties. Barrier properties in one or more layers are important in order to protect the product inside the package from light, oxygen or moisture. Such a need exists, for example, for the protection of foodstuffs, which may run the risk of flavor loss, staling, or spoilage if insufficient barrier properties are present to prevent transmission of such things as light, oxygen, or moisture into the package.
In addition, barrier properties also prevent undesirable leaching of the product to the outside of the bag. For example, oily foods such as potato chips have the potential for some oil to leach out into the film of the bag. The sealant properties are important in order to enable the flexible package to form an airtight or hermetic seal. Without a hermetic seal, any barrier properties provided by the film are ineffective against oxygen, moisture, or aroma transmission between the product in the package and the outside.
A graphics capability is needed because it enables a consumer to quickly identify the product that he or she is seeking to purchase, allows food product manufacturers a way to label the nutritional content of the packaged food, and enables pricing information, such as bar codes to be placed on the product. At the same time, consumers also desire to actually view some products, such as potato chips or tortilla chips, through the packaging film in order generally inspect the food products' physical condition and ensure that most of the product has not been broken into small pieces during transport and handling.
One prior art packaging film used for packaging potato chips and like products is metallized film. Metallized film is typically a polymer film, such as oriented polypropylene (OPP) or polyethylene terephthalate (PET), coated with a thin layer of metal. The thin layer of metal is typically applied using a physical vapor deposition process whereby the metal used for the coating is vaporized and deposited onto a sheet of polymer film, all under vacuum conditions. Prior art metallized film has a shiny, opaque appearance and excellent barrier properties against moisture and oxygen transmission.
FIG. 1 depicts a simplified representation of a prior art apparatus for creating metallized film. Inside a vacuum chamber 100, unmetallized polymer film 202 is disposed on a first roll 208 on one side of the vacuum chamber 100. The unmetallized film 202 is unrolled from the first roll 208, travels through a vapor deposition apparatus 206 where it becomes metallized film 204. As stated previously, the vaporized metal 200 is deposited onto one surface of the film. During the process, the film is continuously unrolled from the first roll 208 and rolled onto a second roll 210 disposed on the side of the vapor deposition apparatus 206 opposite the first roll 208. At the conclusion of the process, the second roll 210 will contain a roll of metallized film 204, while the first roll will be empty.
While metallized film provides food packagers with a relatively inexpensive barrier layer, as mentioned previously, the barrier is opaque. This property can be problematic when used for packages of breakable foodstuffs, such as potato chips or tortilla chips. When shopping for such breakable foodstuffs, some consumers may want to view the contents of the food package before actually purchasing the food package to make sure its contents have not been broken to an undesirable degree. Even for non-breakable foodstuffs, consumers may still want to inspect the contents of a food package before deciding whether to purchase it. Particularly colorful or delicious looking foods may even entice a consumer to purchase them if viewed by the consumer. It would be desirable, therefore, to provide a metallized food packaging film with a viewing window through which the contents of the food package can be viewed.
As described in U.S. Pat. No. 5,530,231, a pattern of oil can be deposited on the polymer film before the vaporized metal is deposited on the film to prevent the deposition of metal on the film in the areas masked by the oil. This masking oil pattern can then be washed off to reveal unmetallized portions of the film underneath. This method suffers from several disadvantages, including substantial increases in processing time and capital expense. Furthermore, this method does not provide any way to control the degree of metallization that occurs on different portions of the film. In other words, a particular portion of film metallized using this method will be either fully metallized or completely unmetallized.
A need exists, therefore, to finely control the degree of metallization over the entire surface of the film, and to do so economically.